fix(app): 修复教练列表页面订单数统计问题

- 在 AppHomeServiceImpl 类中，增加对 categoryId 的空值检查，提高代码健壮性
- 在 AppInstructorMapper.xml 中，修改字段名引用，确保 SQL 查询结果的正确性

national-motion-module-system/national-motion-system-biz/src/main/java/org/jeecg/modules/app/service/impl/AppHomeServiceImpl.java

@@ -212,10 +212,12 @@ public class AppHomeServiceImpl implements IAppHomeService {
      **/
     private List<String> getCategoryName(String categoryId) {
         List<String> list = new ArrayList<>();
-        String[] split = categoryId.split(",");
-        Arrays.stream(split).forEach(id -> {
-            list.add(appCategoryMapper.selectById(id).getName());
-        });
+        if(null != categoryId){
+            String[] split = categoryId.split(",");
+            Arrays.stream(split).forEach(id -> {
+                list.add(appCategoryMapper.selectById(id).getName());
+            });
+        }
         return list;
     }
 

national-motion-module-system/national-motion-system-biz/src/main/java/org/jeecg/modules/system/app/mapper/xml/AppInstructorMapper.xml

@@ -11,7 +11,7 @@
             a.teaching_philosophy,
             a.good_rate,
             a.classes_number,
-            b.user_id,
+            b.id AS userId,
             COUNT( DISTINCT d.user_id, c2.id ) AS orderCount
         FROM
             nm_instructor a
@@ -27,7 +27,7 @@
             a.id,
             b.realname,
             b.avatar,
-            b.user_id,
+            userId,
             c.depart_name,
             a.excel_msg,
             a.teaching_philosophy,